Centrifugal casting machine



Aug. 19, 1958 J. H. LEWIS CENTRIFUGAL CASTING MACHINE Filed Feb. 21, 1956 jolinyfi zjk,

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arrangement United States Patent CENTRIFUGAL CA-STING MACHINE John H. Lewis, Williamsville, N. Y., assiguor to Buffalo Dental Manufacturing Co., Buffalo, N. Y.

Application February 21, 1956, Serial No. 566,945 Claims. (Cl. 22--65.1)

This invention relates generally to the casting art, and more specifically to a new and useful centrifugal casting machine particularly adapted for the casting of small articles of gold or other precious metals such as, for example, inlays or large fillings for dental work.

The general class of centrifugal casting machines with which this invention is concerned comprises those having cross arm means mounted for rotation about an axis and arranged to carry means for casting in response to such rotation. Generally, such cross arms are driven by a spring motor through a one-way clutch, and carry a crucible and mold on one side of the axis and balancing weight means on the other side thereof, whereby upon releasing the spring motor the cross arm is rapidly rotated about the axis, which usually is vertical, and the centrifugal force developed by such rotation drives the molten metal from the crucible into the mold.

It is essential that the molten metal be transferred from the crucible to the mold quickly, before it cools and begins to harden, and also that it be transferred with sufficient force to insure accurate and complete filling of the mold, including any delicate features thereof, and further to insure the complete absence of air pockets in the resulting casting. This is accomplished by suddenly, forcibly rotating the cross arm, as by winding up the spring motor until it is taut and then suddenly releasing it.

However, when the arm begins to rotate theinertia of the molten metal causes it to lag. As a, result, such sudden and forcible rotation of the cross arm causes the molten metal to splash or spill rearwardly from the crucible with the crucible in effect moving out from beneath the metal, whereby a substantial portion of the molten metal is apt to be lostby such spilling which also obviously is inconvenient.

In an attempt to avoid such spilling, it is customary to form the crucible with a relatively high rear side wall, looking in the direction of rotation of the cross arm, to act as a shield. However, this does not solve the problem and spilling continues to occur.

.In a further attempt to solve this problem, machines have been provided having an articulated cross arm with the crucible and mold being carried on a first arm part which is pivoted to a second am part to swing rearwardly about an axis generally parallel to the axis of rotation of the cross arm, under the influence of its inertia, when the cross arm begins such rotation. The intended purpose is to have the crucible and mold react in the same manner as the molten metal to the resultant of the inertial and centrifugal forces acting thereon, with the line of casting moving in alignment with such resultant force. However, it has been found that such machines do not always prevent spilling, and furthermore they are of necessity relatively complicated and expensive.

Accordingly, it is a primary object of this invention to provide a centrifugal casting machine of this general 2,847,738 Patented Aug. 19, 1958 o 44 type which will successfully avoid such spilling of the molten metal.

Another object of this invention is to provide such a centrifugal casting machine which is relatively simple in construction, inexpensive to manufacture, easy to assemble, and highly durable and dependable in operation.

It also is an object of this invention to provide a centrifugal casting machine of this general type having an improved mold and crucible supporting arrangement.

A centrifugal casting machine in accord with this invention is characterized by the provision of cross. arm means mounted for rotation about a first axis and having a portion adapted to support means for casting in response to centrifugal force developed by such rotation, together with means mounting such cross arm portion for swinging movement rearwardly about a second axis extending generally lengthwise of the cross arm.

In another aspect thereof, a centrifugal casting machine in accord with this invention is characterized by the provision of a novel mold supporting arrangement having first bracket means carried by a cross arm and second bracket means carried thereby for movement toward and away from said first bracket means, guide means extending from one of said bracket means into bearing engagement with the other thereof, and means resiliently urging said second bracket means toward said first bracket means.

In still another aspect thereof, a centrifugal casting machine in accord with this invention is characterized by the provision of a novel mold supporting arrangement having first bracket means carried by a cross arm and second bracket means carried by the arm for movement toward and away from said first bracket means, a pair of support members extending from one of said bracket means to the other thereof in spaced relation to the cross arm, and mold support means carried by said support members in suspended relation therebetween.

The foregoing and other objects and advantages of a centrifugal casting machine in accord with my invention will become clearly apparent from the ensuing detailed description of a presently preferred embodiment thereof, taken together with the accompanying drawing illustrating such embodiment wherein:

Fig. 1 is a top plan view of a presently preferred form of centrifugal casting machine in accord with my invention, illustrating the operation thereof;

Fig. 2 is an end elevational view thereof, showing in full lines the position assumed by the mold and crucible when the machine is at rest, and showing in broken lines the position assumed thereby when the cross arm begins rotating;

Fig. 3 is a longitudinal, sectional view thereof taken about on line III-III of Fig. 2; and

Fig. 4 is a fragmentary, perspective view thereof, with the mold and the crucible removed therefrom.

Referring now to the accompanying drawing, the presently preferred form assumed by the centrifugal casting machine of my invention illustrated therein comprises a hollow base 1 containing a horizontally coiled motor spring 2 having its outer end attached to the Wall of the base 1 by the stud 3 and its inner end attached to a first clutchpart 5 by the stud 4. The clutch part 5 cooperates with a second clutch part 6 for driving a generally vertical spindle 7.

The lower end of spindle 7 rests on a ball bearing. 8 carried within a cup-shaped housing 9 which receives the lower end of spindle 7 and which is shouldered, at 11, for being supported by a strap 12 secured across: the bottom of base 1 as by the screws 13. Spindle 7 extends upwardlythrough clutch parts 5 and 6 and outwardly through a ball bearing 14 carried in the upper end of base 1, terminating at its upper end in a rounded, generally bullet-shaped head 15 forming a pivot support for the cross arm generally designated 16.

The foregoing one-way clutch and motor spring drive generally is of a known type wherein the clutch part 6 is fixed to the spindle 7 as by the set screw 17 and has on its under surface a number of ratchet teeth 18 for one way driving engagement with a pin 21 yieldably supported by a spring 22 to project upwardly from the clutch part 5. Therefore, when the spindle 7'is rotated backwards from the direction of the arrow in Fig. 1 a tooth 18 bears against the pin 21 to wind up the spring 2. When the spindle is released, the spring 2 unwinds and the pin 21 transmits rapid rotary motion to the spindle 7, in the direction of the arrow in Fig. 1, through the clutch part 6. Also, when the force of the spring 2 has been spent, rotation of the spindle 13 under its own momentum can continue because the sloping faces between the teeth 18 of the clutch part 6 will ride over the end of the clutch pin 21 and depress it in opposition to the light spring 22 which is of a strength sufiicient only to yieldably hold the pin projected against its own weight.

At its exposed, upper end spindle 7 carries a bifurcated head 23 having a collar portion secured to the spindle for rotation therewith as by the set screw 24 and having a pair of upstanding arms 25 externally threaded to receive a cap 26 thereover and adapted to receive therebetween a cross arm bearing member 27.

The under surface of member 27 is recessed, as at 28, to receive the bullet-shaped pivot 15, and its opposite sides are fiatted, as at 29, for fitting between the flatted inner side walls of the arms 25. Member 27 thereby is confined between arms 25 for rotation therewith, and supports the cross arm 16 for pivoting on the pivot 15 of spindle 7 and for rotation with the spindle 7.

On one side of spindle 7, arm 16 has a weight carrying portion 31 threaded as at 32 and carrying in threaded engagement therewith a weight 33 adjustable thereon. Weight 33 is releasably held in adjusted position as by a jam nut 34 also threaded on the arm portion 32. On the other side of the spindle axis, the arm 16 is bent, as at 35 and 36, to provide a mold and crucible carrying portion 37 which, in its normal position of rest, is vertically offset below the pivot 15.

A first bracket 38 is fixed to the outer end of the crank arm portion 37, as by the set screw 38', and a second bracket 39 is carried by said arm portion 37 on the spindle side of bracket 38 in opposition thereto. Bracket 39 is slidable on arm portion 37 toward and away from bracket 38, and is resiliently urged toward bracket 38 by a spring 41 carried by and extending between the base portions 42 and 43, respectively, of brackets 38 and 39, being secured thereto as by the pins 44.

Bracket 39 is provided with a' generally annular, upstanding part 45 defining an opening 46 therethrough, and with a shelf portion 47 extending inwardly therefrom toward spindle 7. A channel-shaped support 48 is fixed to shelf portion 47, as by screws 49, and carries a crucible 51 of refractory material which slip fits therein. Crucible 51 is formed to provide a trough-like basin 52 leading to an outlet 53 fitting through the opening 46 in the upstanding bracket part 45.

Bracket 38 also has a generally annular, upstanding part 54 defining an opening 55 therethrough, and has a pair of generally semi-circular ears 56 protruding from opposite sides thereof. Ears 56 carry a pair of rod-like support and guide members 57 which extend inwardly toward spindle 7 in substantial parallelism with arm portion 37.

Members 57 extend beyond the upstanding part 45 of bracket 39 in bearing relation therewith to support the same in a generally upright position and to guide it during movement toward and away from bracket 38. Members 57 also carry a mold support 58 of generally semi-cylindrical, concave form having at the opposite sides thereof convex portions 59 which slip-fit over members 57 for suspending support 58 therefrom between the bracket parts and 54.

Support member 58 receives in nesting relation therewith a mold ring 61 which is of tubular form and carries therein investment 62 formed in the usual manner to provide a mold cavity 63 and a tapered sprue 64 leading thereto from the crucible outlet 53. The opening vents the space between bracket part 54 and the investment filled mold.

The operation of this machine is as follows. Normally the various parts are in a position of rest as illustrated in Fig. 3 and in full lines in Fig. 2. First of all the crucible supporting bracket 39 is retracted against the spring 41 to the position thereof illustrated in Fig. 4, which procedure is facilitated by the tabs 67 provided on opposite sides of the base portion 43 for manually grasping the same, and the mold ring 61 containing the investment 62 is placed in the mold support 58. The bracket 39 is then released for movement toward bracket 38 and the mold ring is thus held firmly in place between the vertical faces of the supporting bracket parts 45 and 54. The metal to be cast is placed within the basin 52 of crucible 51, and the cross arm assembly is balanced on pivot 15 by adjusting the position of weight 33 along the arm portion 32. I am nut 34 is used to secure weight 33 in adjusted position, and cap 26 is tightened against bearing member 27 to lock it in balanced position and against movement relative to spindle "i. The motor is then wound up by rotating across arm 16 against spring 2, and when adequate spring tension is provided a pin 65, loosely fitting in a pocket formed in base 1, is pulled upwardly to the position thereof illustrated in broken lines in Fig. 3, to bear against arm 16 and hold it against rotation by spring 2.

The metal in the crucible then is melted, as by a blow torch, and when the metal to be cast is at the proper temperature, the cross arm 16 is rotated slightly away from pin to permit it to drop into pocket 60. Arm 16 then is released and the motor spring provides a sudden, forcible rotation in the direction of arrow 68 in Fig. 1 which causes the molten metal to be cast into the mold cavity 63 in a manner understood by the art.

It is a particular feature of this invention that the mold and crucible supporting arm portion 37 is mounted for rotation about an axis a-a extending generally lengthwise of the arm, whereby upon sudden, forcible rotation of arm 16 by the motor spring 2 thearm portion 37 and the crucible and mold carried thereby are enabled to swing rearwardly and upwardly, in the direction of arrow 69 in Fig. 2 to the position illustrated in broken lines therein, in response to the inertia thereof. The molten metal in crucible 51 therefore is fully supported thereby against the force of inertia as Well as against the force of gravity and remains in the basin 52 of crucible 51 without spilling.

In the presently preferred embodiment illustrated 'herein, the arm portion 37 swings freely in response to inertial forces, or more properly the resultant of inertial and gravitational forces thereon, whereby. the molten metal is at all times cradled in the crucible 51 for casting in response to centrifugal force. In this way, spilling of molten metal is completely avoided without resorting to special crucibles and/ or complicated articulated arm structures. Also, this embodiment of the invention is characterized by rotation of the entire arm 16 which is of one piece construction, about an axis extending generally lengthwise thereof, and by the axis of casting, through crucible outlet 53 into mold sprue 64, being substantially coincident with such lengthwise axis of rotation. While this arrangement is presently preferred, because of its simplicity and because a more perfect casting action seems to result, I contemplate that an arrangement could be provided wherein only the arm a) portion 37 would rotate in response to such inertial forces While retaining the primary feature of this invention, and the casting axis need not be coincident with such lengthwise axis of rotation, or even substantially so, to achieve satisfactory casting.

Stop means can be provided to limit swinging movement of the cross arm portion 37 about axis a-a to substantially only the 90 are required for purposes of this invention as illustrated in Fig. 2. In the illustrated embodiment, such stop means comprise a pin 68 projecting from cross arm 16 into a transverse slot 69 in the bearing member 27.

The mold and crucible supporting arrangement also is a feature of this invention worthy of note. The members 57 support and guide bracket 39, permitting the use of a cylindrical rod for the arm even at the portion 37, and the mold supporting arrangement accommodates molds of different sizes by using supports 58 varying in depth. The mold is supported on the bracket 38 which permits movement of the crucible supporting bracket 39 relative thereto. The mold, mold support and crucible slip into position, whereby placement and removal thereof is facilitated, and the brackets are spring urged into operative relation. For these and other reasons, the entire arrangement lends itself to facile manipulation.

Accordingly, it is seen that the centrifugal casting machine of this invention fully accomplishes the aforesaid objects, and provides a simple and relatively inexpensive, practical construction which provides the desired casting action without spilling the molten metal. It is presently contemplated that the various parts will be made of aluminum, to provide a relatively light weight machine. While only a presently preferred embodiment has been disclosed in detail herein, it will be appreciated that the invention is not limited to the details thereof and that various modifications and variations are possible without departing from the spirit of the invention and the scope of the appended claims.

Having fully disclosed and completely described my invention, together with its mode of operation, what I claim as new is:

1. In a centrifugal casting machine, normally generally horizontal arm means mounted for rotation about a normally generally upright axis, said arm means having an offset portion generally parallel thereto, mold support means carried by said arm portion for casting in response to the centrifugal force produced by such rotation, and means mounting said arm portion for rearward swinging movement about an axis generally parallel thereto in response to the inertial force thereon during such rotation, said support means being movable with said arm portion and being held against swinging movement relative thereto in response to such forces.

2. In a centrifugal casting machine, a norm-ally generally horizontal arm mounted for rotation about a normally generally upright axis, said arm having a generally horizontal offset portion carrying mold support means for casting in response to the centrifugal force produced by such rotation, and means mounting said arm portion for swinging away from the direction of such rotation about an axis extending generally lengthwise of said arm in response to the inertia of said portion and support means when said arm begins such rotation, said support means being movable with said arm portion, and said arm portion and said support means being held against any other swinging movement.

3. In a centrifugal casting machine, an arm mounted for rotation about a first axis, said arm having a portion substantially parallel thereto carrying means for casting in response to the centrifugal force of such rotation, and means mounting said arm portion for swinging movement only rearwardly about a second axis extending at generally a right angle to said first axis in response to the inertia thereof, said support means moving with said arm portion and being held against swinging movement relative thereto.

4. In a centrifugal casting machine, a support member rotatable about a normally generally upright first axis, said member having a normally generally horizontal laterally offset portion, mold support means carried by said portion for casting in response to centrifugal force pro duced by such rotation, and means mounting said support member portion for swinging rearwardly and upwardly about a second axis transverse to said first axis in response to the inertia thereof and of said support means, said support means being movable with said support member portion about said axes and being held against movement relative thereto in response to such inertial and centrifugal forces.

5. In a casting machine, a base, a spindle carried by said base and journalled for rotation about a normally generally upright axis, a support arm, connection means mounting said arm on said spindle for rotation therewith about said generally upright axis, said arm having a normally generally horizontal offset portion movable therewith about said axis andnormally lying below the mounting connection between said arm and said spindle, mold support means carried by said arm portion for casting in response to centrifugal force developed by such rotation, and means mounting said arm portion for swinging rearwardly and upwardly toward the level of said mounting connection in response to the inertia thereof and of said support means at the beginning of such rotation, said support means being movable with said arm portion and being held against movement relative thereto in response to such inertial and centrifugal forces.

6. In a centrifugal casting machine, a base, a spindle journalled on said base for rotation about a normally generally vertical axis, a normally generally horizontal arm, means connecting said arm to said spindle for rotation therewith about said axis, said arm having a normally generally horizontal laterally ofiset portion movable therewith about said axis, mold support means carried by said portion for casting in response to centrifugal force produced by such rotation, and means mounting said arm portion for rearward swinging movement about a normally generally horizontal axis in response to the inertia of said arm portion and support means at the beginning of rotation about said generally vertical axis, said support means being movable with said arm portion about said axes and being held against movement relative thereto in response to such centrifugal force.

7. A centrifugal casting machine comprising, a base, a spindle mounted on said base for rotation about a normally generally vertical axis, a bearing member carried by said spindle for movement therewith about said generally vertical axis, and a cross arm journalled in said bearing member for rotation therewith about said generally vertical axis .and for rotation relative thereto about a normally generally horizontal axis, said cross arm having on one side of said spindle a laterally offset and normally generally horizontal part movable therewith about said axes to swing rearwardly and upwardly about said generally horizontal axis in response to inertial forces upon rotation of said cross arm about said generally vertical axis, and mold and crucible support means carried by said cross arm part for casting in response to centrifugal force produced by rotation of said cross arm about said generally vertical axis, said mold and crucible support means being movable with said cross arm part about said axes and being held against movement relative thereto in response to such centrifugal force.

8. A centrifugal casting machine comprising, support arm means mounted for rotation about an axis transverse thereto, said arm means including a portion carrying mold and crucible support means for casting in response to centrifugal force developed by such rotation, said support means comprising first bracket means fixed on said arm portion, second bracket means carried by said arm portion between said first bracket means and said axis and movable lengthwise of said arm portion toward and away from said first bracket means, said second bracket a relation to each other and to said arm portion, a mold support of generally semi-cylindrical concave form to receive a mold ring in nested relation therewith, said mold support having convex portions at opposite sides thereof and being suspended between said support members with said convex portions slip-fitted thereover, and means resiliently urging said second bracket means toward said first bracket means to clamp a mold ring therebetween.

9. In a centrifugal casting machine, support arm means mounted for rotation about a normally generally upright axis, said arm means having a normally generally horizontal portion carrying mold and crucible support means for casting in response to centrifugal force developed by such rotation, said support means comprising first bracket means fixed to said arm portion for movement therewith and against movement relative thereto, second bracket means carried by said arm portion between said first bracket means and said axis, said second bracket means being movable on said arm portion toward and away from said first bracket means .and being otherwise held against movement relative to said arm portion, a pair of support members extending from one of said bracket means in spaced relation to said arm portion into bearing engagement with the other of said bracket means on opposite sides of said arm portion for guiding said second bracket means in its movement lengthwise of said arm portion, mold support means suspended between said member, means resiliently urging said second bracket means toward said first bracket means to clamp a mold therebetween, and crucible support means carried by said second bracket means.

10. A centrifugal casting machine as set forth in claim 9, wherein said arm portion is mounted for rearward swinging movement about a normally generally horizontal axis in response to inertial forces produced by such rotation, said mold and crucible support means being movable therewith and held against swinging movement relative thereto.

References Cited in the file of this patent UNITED STATES PATENTS Re. 17,783 Gardner Aug. 26, 1930 1,110,954 Maier Sept. 15, 1914 1,142,840 Pankratz June 15, 1915 1,429,807 Turner Sept. 19, 1922 1,496,429 Pollen June 3, 1924 1,554,576 Hale Sept. 22, 1925 1,658,084 Hudson Feb. 7, 1928 1,884,394 Turner Oct. 25, 1932 1,944,435 Kerr Jan. 23, 1934 2,037,617 Carpenter Apr. 14, 1936 2,037,618 Carpenter Apr. 14, 1936 2,140,204 Grifiin Dec. 13, 1938 2,265,043 Moore Dec. 2, 1941 2,433,065 Rubissow Dec. 23, 1947 2,752,650 Bosna July 3, 1956 FOREIGN PATENTS 70,734 Austria Dec. 17, 1915 619,238 Great Britain Mar. 7, 1949 

